1. Field of Invention
The invention relates to membrane keyboards and more particularly to a back lighted membrane keyboard having components being secured together by subjecting to ultrasonic welding.
2. Description of Related Art
Laptops are widely used by people throughout the world due to portability, word processing and other capabilities common to desktop computers, and Internet access. Membrane keyboards are typically employed by laptops. Membrane keyboards are advantageous for being thin, lightweight, and compact. However, most types of laptops are limited to operate in a bright environment only since there is no backlight device provided.
For overcoming above drawback, many prior keyboard/keypad patents with backlight arrangement are disclosed. For example, Taiwanese Utility Model Patent No. M306,689 discloses a keyboard with backlight arrangement. Also, in my earlier U.S. Pat. No. 7,608,792, an improved membrane keyboard/keypad with arrangement for uniformly lighting keys from background is disclosed.
The U.S. Patent has been successfully used in a commercial application. However, in practice it is found that components of the U.S. Patent are not always aligned since they are assembled by adhesive. This adversely lowers the yield. Thus, continuing improvements of membrane keyboards for laptop are constantly sought by the present inventor.